Power transformers in a transmission substation raise the voltage from the generation voltage to transmission levels.

• A. False
• B. They lower the voltage
• C. True
• D. They regulate frequency

Answer: (C)

Raising voltage for long-distance transmission is what power transformers in a transmission substation do. They use the turns ratio to increase the generation voltage to a higher transmission level while keeping the power roughly the same. Higher voltage means lower current for the same power, which reduces I^2R losses in the lines and makes sending power over long distances more efficient. The grid’s frequency is set by the generators and overall system design, not by the transformer, so transformers don’t regulate frequency. They also don’t lower voltage at this point—step-down transformers handle voltage reduction closer to customers.